Factory automation (FA) technology involving controllers, such as programmable logic controllers (PLCs), is widely used at various production sites. A potential need for such controllers is to increase capacity utilization and maintainability by reducing the equipment downtime and maintenance time. Japanese Unexamined Patent Application Publication No. 2015-133002 (Patent Literature 1) describes, for example, an instrumentation system that prevents a decrease in capacity utilization and maintainability in a system including a non-redundant multipoint I/O module. More specifically, Patent Literature 1 describes a host control device that operates a non-redundant I/O module in a pseudo-redundant manner. When the I/O module is to be replaced, the host control device transfers control to a new I/O module.